The present invention relates to a key switch for use in the keyboard of an electronic cash register, a personal computer, or the like, and more particularly to a coil spring incorporated in such a key switch.
As shown in FIG. 1 of the accompanying drawings, a conventional key switch of the type described is composed of a guide cylinder 9 fixed to a key attachment plate 90, a key plunger 91 reciprocally movably disposed in the guide cylinder 9, a spring seat 93 of silicone rubber fitted in the lower opening of the guide cylinder 9, a first coil spring 94 disposed on the spring seat 93 in the guide cylinder 9 for returning the key plunger 91 upwardly, a second coil spring 95 for pushing downwardly a central switch actuator 92 on the spring seat 93, and a key top 96 mounted on the upper end of the key plunger 91. Since the illustrated prior key switch requires two coil springs, it has been necessary to individually stack separate coil springs.
For assembling the key switch on the key attachment plate 90, the key plunger 91 and the coil springs 94, 95 are first inserted into the guide cylinder 9 through its lower opening, then the spring seat 93 is fitted in the lower opening of the guide cylinder 9, and finally the key top 96 is fitted over the upper end of the key plunger 91 which projects upwardly from the guide cylinder 9. Since it is necessry to assemble the key switch on both sides of the key attachment plate 90, assembly efficiency is low, and it is difficult to increase the number of switches or change the arrangement of switches. With the illustrated key switch, furthermore, there are required a total of six parts, including the guide cylinder 9, the key plunger 91, the spring seat 93, the two coil springs 94, 95, and the key top 96. During assembly, therefore, the parts are required to be positioned for the attachment of each coil spring, resulting in various practical problems such as a complex assembling process, a low assembling efficiency, and a complicated stock of parts.